Disk eject error msg -- Final follow-up

Edit: see final follow-up post below

In the past month our home has experienced two brief power outages related to thunderstorms. In both cases there were notifications on my Mac Studio: “disk not ejected properly”, referring to my Novus 8TB External USB-C Rugged Desktop Hard Drive. Link: https://oyendigital.com/novus-8tb-external-usb-c-rugged-desktop-hard-drive.html

The computer and external HDD power cables are connected to a Cyberpower LE850G Battery back up (https://www.cyberpowersystems.com/product/ups/battery-backup/le850g/).
This unit is relatively new, purchased about 8 months ago.
The computer and the disk drive operate normally after the power loss episodes. There is no lost data, no re-boot of the computer, all apps run normally. The external HDD is dedicated to Time Machine backups. Spot checks of the backup data are normal.

In both instances cited above, power was restored within two minutes by my home standby generator. Normal utility-company power was restored after 1-2 hours.

Is it “normal” for the disk not ejected properly message appear simply from switching from line power to battery UPS power, then quickly back to line power? Does this indicate that my LE850G Battery back up is insufficient and that I need a different/larger UPS/battery backup?

Edited to add: There are also two Apple Studio Display Monitors connected to the same LE850G Battery back up, in addition to the Mac Studio and Novus 8TB external HDD. Power consumption of Mac Studio (M1 Max): 11W - 115W. Power consumption of each Studio Monitor: 30W. I assume that the total power consumption of devices connected to the battery backup power supply is well within the rated specification for the battery backup power supply.

The unit you link to has two sets of outlets, only six of which have battery backup. All twelve have surge protection. Have you confirmed the hard drive is plugged into a battery backup outlet?

Yes, connected to battery backup outlet. And I confirmed that the battery backup unit supplies power immediately when the main power fails. The LED desktop light remains on, does not flicker. Computer and monitors remain on also.

Actually all of the devices (Mac Studio, 2 Studio Displays, external HDD, small LED desktop lamp) are plugged in to a very heavy-duty power strip/surge suppressor mounted under the desktop. The power strip cable is plugged in to the battery backup side of the battery backup unit.

Hmmm … the manual states:

" 4. Plug the UPS into a 2 pole, 3 wire grounded receptacle (wall outlet). Make sure the wall branch outlet is protected by a fuse or circuit breaker and does not service equipment with large electrical demands (e.g. air conditioner, refrigerator, copier, etc.). The warranty prohibits the use of extension cords, outlet strips, and surge strips in conjunction with the UPS unit."

[emphasis added]

Perhaps try plugging your equipment directly into the UPS unit and then simulating an outage event.

To me this suggests that the unmounting may have occurred when power was restored.

Good thought. It may take a few days for me to try this, as all devices are mounted on a moveable standing desk with extensive cable management to minimize clutter. If above testing suggests a new configuration, the heavy battery backup unit would have to be secured to the bottom of the desktop. See photo. Currently the battery backup unit is on the floor beside the cabinet to the right of the desk.

Another good thought. Will have to test for that. If this is true, I would probably want to make a new policy to disconnect the external HDD immediately after a power failure and wait to re-connect until main power is restored.

I would expect the power to be a bit erratic for a short time after restoration, due to various loads being reapplied. Your backup generator might contribute to that as well.

Also, I wouldn’t be surprised if the computer is more sensitive to power fluctuations than the UPS.

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Follow up (from original poster):

It appears that the disk eject error messages may not be due to the battery backup/UPS unit after all. After returning from a short trip during which the Mac Studio and peripherals were powered down, 2 additional disk eject error messages appeared a few hours after powering up the Mac. There were no power interruptions during that time.

It appears that many Mac users using Big Sur and Monterrey have reported disk eject error messages using various different types of Macs and disk drives. See link from Apple Developer forums: https://developer.apple.com/forums/thread/679836

Before dismantling my cable management setup I will do more observation and simple tests, including ensuring that data and power cables are good and securely installed, etc. One user in the above forum posted a simple solution: after booting up with an external disk drive, properly eject and then re-connect that drive.

Stay tuned …


At the risk of jinxing myself … I have 10 external drives and have not experienced this issue. Both HD and SSD, from several manufacturers, standalone and in enclosures.

I wonder if there could be an issue with the drive?

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That is possible, of course. That will be tested that by connecting the drive at various times to each of the four Macs running different versions of macOS or OS-X available to me. But first I will determine if the simple steps of ejecting then reconnecting the disk drive after each power-down boot-up solves the problem (as it did for another user).

I also have used multiple different disk drives over several years using several Mac computers. The only disk eject messages previously encountered were related to the connecting cable of a cheap portable drive.

After (mostly but not conclusively) ruling out the battery-backup unit as the cause, a problem with the drive itself (or its data cable or power cable) seemed to be the most likely culprit. Then I saw the Apple Developer Forum thread in which there are many reports of the problem with many different disk drives … etc.

That brought me back to the possibility of a macOS bug, so all bets are off.

All possibilities must be explored, so let the games begin … . This will take some time.

And you could probably automate this with a script that runs at start up.

Good luck and happy troubleshooting!

disk eject error messages - disk not ejected properly…

I have been told that hardware damage can occur if the disk is writing at this time. If it has been idle - then maybe no damage occurred…

Would anyone confirm this point?

To the best of my knowledge, hardware damage would be very unlikely. You might lose everything on the disc due to data corruption though.

Followup for those interested. Thank you to @MevetS and @jec0047 for your replies.

@MevetS - your suggestion that the external disk drive itself could be the problem was correct, thank you. Not specifically the disk drive, but the disk drive’s USB-C connector. The temporal association with power outages and switch to backup power was a red herring. Reminder note to myself: Association is not causation.

Troubleshooting steps (some mentioned above) ruled out the UPS/battery backup, the power adapter/cable, data cable and computer’s USB-C port as the cause of the problem. Ultimately the problem was isolated to the disk drive, since error messages appeared with the drive connected to another computer.

Oyen Digital replied within two hours after submission of an online support request and explanation of the problem and troubleshooting steps. The representative stated that the problem was the USB-C connector within the disk drive. A new disk drive was shipped the next day, along with a prepaid shipping label to return the defective drive. The new drive works perfectly, and there have been no error messages after the first 24 hours.

Based on my experience so far I can recommend the Oyen Digital 8TB external HDD and enclosure. This disk drive was one of those recommended by Mike Bombich of Carbon Copy Cloner. See this link:
The drive is fast (much faster than the ubiquitous inexpensive “portable” HDDs). Customer Service is excellent.

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